EP3156784A1 - Caractérisation améliorée de propriétés diélectriques - Google Patents

Caractérisation améliorée de propriétés diélectriques Download PDF

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Publication number
EP3156784A1
EP3156784A1 EP15189446.6A EP15189446A EP3156784A1 EP 3156784 A1 EP3156784 A1 EP 3156784A1 EP 15189446 A EP15189446 A EP 15189446A EP 3156784 A1 EP3156784 A1 EP 3156784A1
Authority
EP
European Patent Office
Prior art keywords
sensor
under test
electromagnetic radiation
sensor according
material under
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP15189446.6A
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German (de)
English (en)
Inventor
Johan Stiens
Vladimir MATVEJEV
Gokarna PANDEY
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
M2wave bvba
Vrije Universiteit Brussel VUB
Original Assignee
M2wave bvba
Vrije Universiteit Brussel VUB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by M2wave bvba, Vrije Universiteit Brussel VUB filed Critical M2wave bvba
Priority to EP15189446.6A priority Critical patent/EP3156784A1/fr
Priority to PCT/EP2016/074523 priority patent/WO2017064153A1/fr
Publication of EP3156784A1 publication Critical patent/EP3156784A1/fr
Withdrawn legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N22/00—Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G01R27/2617—Measuring dielectric properties, e.g. constants
    • G01R27/2635—Sample holders, electrodes or excitation arrangements, e.g. sensors or measuring cells
    • G01R27/2658—Cavities, resonators, free space arrangements, reflexion or interference arrangements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G01R27/2617—Measuring dielectric properties, e.g. constants

Definitions

  • the invention relates to the field of sensing. More specifically it relates to methods and systems for sensing dielectric properties of materials using reflection or transmission measurements.
  • the dielectric permittivity of a material depends on particular properties such as for example its composition and its temperature. Since physical changes such as moisture loss, protein denaturation, etc. take place during processing for example industrial processing and since these affect the dielectric properties of materials, the process or thereof can be followed by monitoring or evaluating changes in dielectric permittivity.
  • Monitoring or evaluating changes in dielectric permittivity may for example be performed using an electromagnetic measurement system or sensor.
  • An electromagnetic measurement system or sensor for measuring dielectric properties changes in material is based on detection of electromagnetic wave reflection coefficients.
  • Existing sensor solutions measure changes in the reflection coefficient to determine the material properties (e.g. moisture, temperature, overall composition, and etc.). Nevertheless, the changes in reflection coefficient due to material property changes are small and often cannot distinguish subtle change.
  • Existing electromagnetic sensor solutions like free-space electromagnetic measurements often use a simple antenna configuration, as shown in FIG. 1 .
  • Open resonators, like a Fabry-Perot require the material under test (MUT) to be loaded into the resonator, as shown in FIG. 2 , this imposes conditions on sample size, placement.
  • MUT material under test
  • open-ended electromagnetic transmission-lines can be used for material characterization as shown in FIG. 3 , but these solutions also do not feature high sensitivity, while transmission line resonators need to be loaded with the material under test (MUT) inside the transmission line.
  • MUT material under test
  • FIG. 4 Yet another known configuration is given, wherein a waveguide configuration is used in FIG. 4 .
  • the sensors shown in FIG. 1 and FIG. 3 are wideband but are little sensitive to changes of the dielectric permittivity of the material.
  • the sensors in FIG. 2 and FIG. 4 utilize a resonator to enhance the sensitivity of a conventional open-ended probe.
  • a thin layer of MUT is in direct contact with the resonator and is covered with metal, which imposes limitations on MUT.
  • a sensor system and method can be obtained whereby a process, e.g. industrial process can be followed by instantaneous detection of the changes in dielectric permittivity of a material, using reflection or transmission measurements.
  • the present invention relates to a sensor for sensing a reflection or transmission property of a material, the sensor comprising an electromagnetic radiation input means for creating or receiving an electromagnetic radiation signal, a resonator for influencing the electromagnetic radiation input signal, a material holder for holding the material under test, a delay line positioned between the resonance filter and the material holder such that the electromagnetic radiation travels in the delay line after passing the resonance filter and prior to reaching the material under test, when it is positioned in the material holder, and a detection means for detecting a signal reflected by or transmitted through the material under test. It is an advantage of embodiments according to the present invention that small changes in the reflection properties of a material under test, result in larger changes of the reflection coefficient or transmission coefficient measured for the material under test using the particular configuration of the resonance filter, the delay line and the material holder.
  • the sensor may have a free space configuration. It is an advantage of embodiments according to the present invention that a free-space configuration can be used, whereby little or no limitative conditions are posed on the material under test.
  • the electromagnetic radiation input means may be an electromagnetic radiation source comprising a transmitter.
  • the sensor may have a waveguide-based configuration, wherein the electromagnetic radiation input is a waveguide portion wherein electromagnetic radiation can be coupled and wherein the resonance filter is a resonance filter embedded in the waveguide and wherein at least part of the delay line is positioned in the waveguide. It is an advantage of some embodiments of the present invention that for some applications a waveguide-based configuration can be used.
  • the system may comprise a transceiver, functioning both as electromagnetic radiation input means and as detection means.
  • the resonator may be a high quality factor resonator, with a quality factor larger than 10.
  • the resonator may be a band pass filter.
  • the length of the delay line may be adjustable so as to be able to adjust the sensor to the material under test to be measured.
  • the material holder may be adapted for adjusting a position of the material under test, so as to adjust the length of the delay line.
  • the present invention also relates to the use of a sensor as described above for detection a change in dielectric properties of a material under test.
  • the present invention furthermore relates to the use of a sensor as described above for monitoring a change in material composition.
  • the present invention also relates to the use of a sensor as described above for monitoring a process, e.g. an industrial process.
  • reference is made to a material under test or MUT reference is made to the material of interest that is to be identified based on dielectric properties or that is to be monitored for identifying properties of the material during a process, e.g. an industrial process, or that is to be monitored for identifying properties of the process, e.g. an industrial process.
  • the material under test or MUT has a reflection coefficient larger than zero.
  • the reflection coefficient S11 should be larger than 0.
  • the present invention relates to a sensor for detecting a dielectric property of a material under test or a change in dielectric properties of a material under test.
  • the dielectric property may for example be a permittivity of a material, a real and/or imaginary dielectric permittivity, a loss tangent, a real and/or imaginary refractive index, relaxation parameters for a dielectric permittivity model such as a Debye, Cole or HVeronicaiak-Negami model whereby the relaxation parameters can for example be time constants or strength, etc.
  • the dielectric property is based on a reflection or transmission measurement of the material under test.
  • a configuration is used for measuring reflection or transmission whereby small changes in the reflection or transmission properties of the material under test result in significantly larger changes in the overall reflection or transmission measured, such that detection with a high sensitivity can be used.
  • Changes in dielectric properties can be caused by changes to the material under test and consequently, the systems and methods of the present invention allow to detect or follow material changes.
  • systems and methods may be suitable for monitoring environmental changes or processes, such as for example industrial processes.
  • the senor comprises an electromagnetic radiation input means for creating or receiving an electromagnetic radiation signal.
  • an electromagnetic radiation input means may be an electromagnetic radiation source allowing generation of electromagnetic radiation, or it may be a receiving means adapted for receiving an electromagnetic radiation, such as for example a waveguide portion adapted for receiving electromagnetic radiation from a source.
  • the radiation source -which may be part or may not be part of the sensor - may be a conventional radiation source emitting electromagnetic radiation at least at frequencies where the reflection/transmission is most sensitive.
  • the radiation source may for example be an oscillator such as for example backward wave oscillators, IMPATT diodes, Gunn diodes, etc., it may for example be a non-linear frequency converters or Multipliers such as harmonic mixers, balanced mixers, etc., it may be for example a phase locked synthesizer, a voltage controlled oscillator or a nonlinear optical mixer (optics to THz).
  • the frequency range wherein the reflection is measured may depend on the size of the object.
  • the frequency range may be in a microwave frequency range, e.g. between a few MHz up to 10 GHz, which can for example be used for bulky objects, may be in the millimeter wave range, e.g. between 10GHz to 100GHz, or may be in the Terahertz range, e.g. between 100 GHz to 10THz.
  • the radiation source may comprise a radiation antenna. It may be a transmittor or may be a transceiver.
  • the sensor furthermore comprises a resonator for modifying the electromagnetic radiation input signal.
  • the resonator may be a high quality factor resonator.
  • the resonator may be a band pass filter.
  • the resonator may be one or more resonant elements.
  • the resonator may be a band-stop filter.
  • the resonator has a quality factor Q larger than 10.
  • the resonance frequency of the filter typically is in the frequency range of interest.
  • the resonator may be under-coupled, critically coupled, or over-coupled. In some embodiments, resonance is caused by the multiple reflections/transmissions at the edges of the resonator.
  • the sensor also comprises a material holder for holding the material under test (MUT).
  • the material holder may for example be a sample stage, a holder having fixing means for fixing the material on the holder, etc.
  • the material holder allows for displacing the material under test, so that the length of the delay line (which will be further discussed below) can be adjusted.
  • the sensor according to embodiments of the present invention also comprises a delay line.
  • the delay line is positioned between the resonator and the material holder such that the electromagnetic radiation travels in the delay line after passing the resonance filter and prior to reaching the material under test, when it is positioned in the material holder.
  • the delay line may have a length g between the resonator and MUT, which may be selected as function of a dielectric property of the material under test, the thickness of the material under test and the operating frequency used.
  • the length of the delay line may for example be a function of the permittivity of the material measured.
  • the sensor furthermore typically comprises an electromagnetic radiation detection means for detecting radiation reflected by the MUT, after again passing through the delay line and the resonator.
  • the detection means may be any suitable type of detection means, such as for example broad-band detectors like Schottky Diode detectors or narrow-band detectors like I/Q mixers, subharmonic mixers, etc.
  • the detection means may comprise or be a receiver.
  • the source and the detector may comprise common parts, for example a transceiver may be present allowing to emit the electromagnetic radiation towards the MUT and allowing to detect reflected or transmitted electromagnetic radiation.
  • the sensor furthermore may comprise a processing means or processor for converting a detected reflection signal in a dielectric parameter of the MUT.
  • a processing means or processor may be part of the sensor or may be external thereto.
  • a processor may comprise or be replaced by a programmed algorithm or a look up table.
  • Other optional component such as for example a memory, processing means, an output means or display for indicating a result, ... may be present, as known by the person skilled in the art.
  • FIG. 5 An example of the configuration of a sensor according to an embodiment of the present invention is shown in FIG. 5 . An electromagnetic radiation source is shown, as well as a resonator.
  • the resonance in the resonator typically may be caused by multiple reflections on the resonator edges (E1 and E2) whereby the specific resonance induced is determined by the reflections on the edges and the resonator length.
  • the high sensitivity of the sensor is obtained as follows : small changes of ⁇ E3 result in a change in resonator conditions which detunes the resonance and causes a bigger signal change.
  • the resonator conditions thereby may be selected such that preferably a high Q factor of the resonator is obtained, that there is a good band pass reflection response and that it corresponds with a multiple of a half-wave or quarter-wave standing wave.
  • the reflection sensor is a free space sensor comprising a resonator and a delay line in the optical path between the radiation source and the material under test.
  • the free space sensor may be especially suitable for some applications, as it imposes little or no limitations on the shape or other properties of the material under test.
  • the material under test can be any type of material for which dielectric properties are of interest. In advantageous embodiments, the evolution of a material under study can be monitored or followed over time.
  • FIG. 6 An example is shown in FIG. 6 .
  • the reflection sensor is a waveguide based sensor wherein the electromagnetic radiation is directed to the material under test using a waveguide.
  • the type of waveguide that can be used is a hollow metal pipe waveguide with various cross-sections, such as rectangular, circular, ridge waveguides, etc., parallel plate waveguides, co-planar waveguides.
  • transmission lines can be used such as for example coaxial cable transmission lines, micro-strip liens and strip lines, ....
  • the resonator can be a waveguide section or transmission line section with some dielectric object inserted with different dielectric permittivity than the rest of the waveguide or transmission line, a waveguide section or transmission line section with a different cross-section and specific length, a waveguide section or transmission line section that is linked to other waveguide through coupling windows, a combination of these implementations, etc.
  • the characteristics of the resonator may be the same as described above.
  • a delay line is present between the resonator and the open-ended waveguide side directed to the material under test.
  • the delay line may be formed by a non-filled portion of the waveguide, between the resonator and the end of the waveguide.
  • the resonator may be positioned at the edge of the open end of the waveguide pointing towards the material under test and the delay may be formed by an open region between the end of the waveguid and the material under test.
  • the delay line is formed by a delay line embedded in the waveguide in combination with an open space between the open-end of the waveguide and the material under test. Such a delay line may have a predetermined length, such that the distance between the resonator and the material under test is appropriate. An example of such a configuration is shown in FIG. 7 .
  • FIG. 8a illustrates the reflection coefficient that is obtained with a reflection measurement configuration according to the state of the art, shown in FIG. 1 , illustrating that the differences in moisture content results in differences small changes in the reflection coefficient, e.g. smaller than 0,2 dB for some moisture changes of 2 to 3%. Nevertheless, for the same moisture changes, the differences in reflection coefficient meaured with a system according to an embodiment of the present invention results in a few dB up to more than 10 dB (depending on the specific moisture content). The latter illustrates that reflection measurements according to embodiments of the present invention result in a far better sensitivity to changes in the corresponding dielectric properties. It is to be noticed that the sensitivity of the sensor typically occurs for a selected frequency of frequency band and is not present over the full frequeny range. Nevertheless, the system can be easily tuned to such a frequency or frequency band.
  • FIG. 9 illustrates the effect on transmission for a liquid as function of the percentage alcohol comprised in the liquid. It can be seen that large differences can be seen in the transmission results that are obtained for alcohol concentrations between 10% and 40%.
  • the present invention also relates to an optical measurement device for sensing pH or pH differences.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
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  • Life Sciences & Earth Sciences (AREA)
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EP15189446.6A 2015-10-12 2015-10-12 Caractérisation améliorée de propriétés diélectriques Withdrawn EP3156784A1 (fr)

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Application Number Priority Date Filing Date Title
EP15189446.6A EP3156784A1 (fr) 2015-10-12 2015-10-12 Caractérisation améliorée de propriétés diélectriques
PCT/EP2016/074523 WO2017064153A1 (fr) 2015-10-12 2016-10-12 Caractérisation améliorée de propriétés diélectriques

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EP15189446.6A EP3156784A1 (fr) 2015-10-12 2015-10-12 Caractérisation améliorée de propriétés diélectriques

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115060978A (zh) * 2022-06-28 2022-09-16 电子科技大学 一种基于时域分析法的介电常数估计方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2021015074A (ja) * 2019-07-13 2021-02-12 マイクロメジャー株式会社 非接触式水分計及び含水率の測定方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3851244A (en) * 1973-12-18 1974-11-26 Electronic Ass Of Canada Ltd Microwave moisture measuring apparatus
US6204670B1 (en) * 1997-06-09 2001-03-20 National Research Development Corp. Process and instrument for moisture measurement
GB2471024A (en) * 2009-06-11 2010-12-15 Wivenhoe Technology Ltd Determining dielectric properties of a material
WO2013164627A1 (fr) * 2012-05-02 2013-11-07 Heriot-Watt University Capteur avec cavité à hyperfréquence
US20150168314A1 (en) * 2013-11-11 2015-06-18 3R Valo, société en commandite Microwave resonator sensor and associated methods of sensing

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3851244A (en) * 1973-12-18 1974-11-26 Electronic Ass Of Canada Ltd Microwave moisture measuring apparatus
US6204670B1 (en) * 1997-06-09 2001-03-20 National Research Development Corp. Process and instrument for moisture measurement
GB2471024A (en) * 2009-06-11 2010-12-15 Wivenhoe Technology Ltd Determining dielectric properties of a material
WO2013164627A1 (fr) * 2012-05-02 2013-11-07 Heriot-Watt University Capteur avec cavité à hyperfréquence
US20150168314A1 (en) * 2013-11-11 2015-06-18 3R Valo, société en commandite Microwave resonator sensor and associated methods of sensing

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115060978A (zh) * 2022-06-28 2022-09-16 电子科技大学 一种基于时域分析法的介电常数估计方法

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